The invention relates to the internal-combustion engines of motor vehicles, and it more particularly concerns a device for regulating the cooling of such an internal-combustion engine.
In present-day motor vehicles with an internal-combustion engine, the cooling device comprises a cooling circuit traversed by a fluid, which is generally water with the addition of antifreeze. The circuit is coupled to a fluid pump in order to cool the internal-combustion engine the operation of which is defined at any moment by a prevailing load and a rotational speed. Moreover, this cooling circuit feeds an installation for heating and/or air conditioning the passenger compartment of the vehicle, with adjustable air-heating parameters, including an air heater.
The fluid pump is usually driven mechanically by the crankshaft of the engine, such that the throughput of the pump depends directly on the rotational speed of the engine. It results therefrom that the energy which is taken up by the pump from the engine shaft is not optimised. In fact, this energy is generally very much greater than that required. Consequently, on the one hand, energy from the engine is consumed needlessly, resulting in an over-consumption of fuel, and, on the other hand, the engine, and particularly the oil of its oil circuit, is overcooled, resulting in an increase in friction and consequently a lowering of the efficiency of the engine.
An object of the invention is to at least partly mitigate these drawbacks.
According to the present invention there is provided a device for regulating the cooling of a motor-vehicle internal-combustion engine, of the type comprising a fluid-cooling circuit coupled to a fluid pump for cooling the said internal-combustion engine the operation of which is defined at any moment by a prevailing load and a rotational speed, the said circuit feeding an installation for heating and/or air conditioning the passenger compartment of the vehicle, with adjustable air-heating parameters, including an air heater, the device further comprising:
means for establishing an engine-starting state on the basis of chosen conditions; and
means which are active in this starting state so as, depending on a quantity representative of the heating demand and on at least one other quantity,
either to stop the pump if the heating demand is below a certain threshold,
or else to drive the pump as a function of a saturation rotational speed.
Thus, the invention envisages regulating the cooling of the internal-combustion engine in an engine-starting state, which corresponds to a phase in which the engine is cold, also called start-up phase.
Hence, the device of the invention first of all determines whether the engine is in its starting state and, if so, it stops or drives the pump as a function of a quantity representative of the heating demand, and of at least one other quantity.
It results therefrom that the device calculates the minimum throughput of the pump which is necessary for the engine to be cooled at the instant of the calculation. It is thus also possible optimally to regulate the throughput of the pump, and consequently the cooling of the engine, during this starting state.
The device according to the invention may comprise other complementary characteristics capable of being taken separately or in combination, and especially:
the means for establishing the engine-starting state comprise means for detecting the operation of the engine and means for measuring or estimating a temperature representative of the thermal state of the engine and comparing it with a given threshold, so as to establish the starting state when this temperature is below this threshold;
the means for detecting the operation of the engine comprise a sensor for detecting whether the contact of the engine is open and a sensor for detecting whether the rotational speed of the engine exceeds a given threshold;
the temperature representative of the thermal state of the engine is a temperature of the material of the engine;
the temperature representative of the thermal state of the engine is a temperature of the fluid leaving the engine;
the temperature representative of the thermal state of the engine is a temperature of the fluid in the engine;
the temperature representative of the thermal state of the engine is a temperature of the lubricating oil of the engine;
the quantity representative of the heating demand is a heating position defined by a value in terms of a percentage of the maximum heating demand, and the active means moreover receive a quantity representative of a temperature discrepancy between the temperature of the fluid leaving the engine and the temperature of the ambient air;
the active means comprise control means suitable for stopping or driving the pump as follows:
if the heating demand is zero or below the threshold, then stopping the pump,
if the heating demand exceeds the threshold, then
if the temperature discrepancy is below a first threshold, stopping the pump;
if the temperature discrepancy is above the first threshold and below a second threshold, driving the pump by establishing the rotational speed of the pump at a value proportional to the saturation rotational speed which corresponds to the rotational speed of the pump making it possible to obtain a saturation throughput in the air heater;
if the temperature discrepancy is above the second threshold, then driving the pump by establishing the rotational speed of the pump at a value equal to the saturation rotational speed;
the other condition is related to a temperature of a material representative of the thermal state of the engine;
in the case in which the material temperature is available, the device comprises comparison means for comparing the material temperature with a given threshold, and
if the material temperature is below this threshold, then for activating the said active means,
if the material temperature is above this threshold, then for de-activating the said active means and establishing the pump rotational speed just at a value necessary for the correct operation of the engine, having regard to the prevailing load and the rotational speed of the engine;
in the event that the material temperature is unavailable, the device comprises estimating means for estimating this material temperature;
these estimating means are chosen from among:
an internal-combustion engine model which calculates the material temperature as a function of an engine rotational-speed and engine-load log,
a table of correlation between the temperature of the lubricating oil of the engine and the material temperature, and
a table of correlation between the temperature of the fluid leaving the engine and the material temperature;
in the event that the material temperature is unavailable, the device comprises means such that, as soon as the rotational speed of the engine has exceeded a given threshold, the pump is stopped for a fixed period, then operates at a minimum throughput as long as the temperature of the fluid leaving the engine is below a given threshold; and
in the event that the material temperature is unavailable, the device comprises means such that, as soon as the rotational speed of the engine has exceeded a given threshold, the pump operates at a minimum throughput as long as the temperature of the fluid leaving the engine is below a fixed threshold.